1. Field of the Invention
The present invention relates to a process for securing particulate bulk loads in motor coasters and ocean-going vessels.
2. Description of the Prior Art
Raw materials and finished products are increasingly being transported as bulk loads. This is true of both river and seaborne transport. In the days of the sailing ship, it was in particular grain which was shipped in bulk. Nowadays, about 25% of the world's merchant tonnage is available as bulk carriers for transporting coal, ores, grain, minerals, salts, fertilizers and other materials in bulk form.
A precondition for this very economical type of transportation is that the products should be reasonably insensitive to weather factors, so that it is possible to dispense with packaging, for example in sacks, which in particular provides protection against moisture. Whilst this property is a precondition for preserving the quality of the goods, there are other properties which are of considerable importance for the safety of the ship and its crew.
These properties concern the resistance which granular bulk material offers to the relative shift of its particles, that is to say concern the problem that bulk loads can, during sea transportation, start to slip as a result of vibration and above all as a result of the list of the vessel about its longitudinal axis. The sliding resulting from the list leads to a shift in the load and hence to a shift in the center of gravity of both the load and the vessel, with all that this implies regarding the stability of the vessel.
In the past, many grain clippers were lost due to their loads shifting. Even at the present time, motor vessels still capsize for this reason in heavy seas, and fast ships are endangered by hard corrections of their course, even in calm seas.
In order to counter these hazards which arise when shipping bulk loads, the loose cones of the load are trimmed more or less flat before leaving port. As a result, the danger of a transverse shift in the load is, ideally, avoided up to an angle of list of the ship which approximately corresponds to the natural angle of repose of the particular bulk material. If the ship is piloted expertly, angles of list above a maximum value of about 35.degree. will not occur, and bulk materials having a natural angle of repose above this maximum value can be transported safely.
Bulk goods having a low natural angle of repose require additional measures. The relevant guidelines recommend plane trimming and, where necessary, fitting of longitudinal bulkheads into the holds. Certain products, such as grain, exhibit special flow of the moving material. With such goods, a shift in the load is also hindered by loading the trimmed surface by means of stacks of bagged material several meters high. These steps--especially the longitudinal bulkheads which may have to be fitted--adversely affect the economics, and hence the benefits, of bulk loading. An additional fact is that only a few goods, such as grain, can be unloaded pneumatically; if, on the other hand, unloading is to be by means of grabs, the temporary auxiliary bulkheads in general greatly hamper unloading.
In addition to taking the measures described, shifts in loads can also be reduced by suitable construction of the ships. Thus, at the present time, bulk freighters can be built to be, in a sense, self-trimming, by matching the shape of the holds to the angle of repose of the load. This construction proves of value in special ships for bulk loads having a particular bulk density which always remains the same. However, the construction is ineffective if, for example, the hold is only half-filled or if bulk loads of different bulk density, in particular of higher bulk density, are involved.